drm/xe/vf: Don't try to trigger a full GT reset if VF

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/xe/vf: Don't try to trigger a full GT reset if VF VFs don't have access to the GDRST(0x941c) register that driver uses to reset a GT. Attempt to trigger a reset using debugfs: $ cat /sys/kernel/debug/dri/0000:00:02.1/gt0/force_reset or due to a hang condition detected by the driver leads to: [ ] xe 0000:00:02.1: [drm] GT0: trying reset from force_reset [xe] [ ] xe 0000:00:02.1: [drm] GT0: reset queued [ ] xe 0000:00:02.1: [drm] GT0: reset started [ ] ------------[ cut here ]------------ [ ] xe 0000:00:02.1: [drm] GT0: VF is trying to write 0x1 to an inaccessible register 0x941c+0x0 [ ] WARNING: CPU: 3 PID: 3069 at drivers/gpu/drm/xe/xe_gt_sriov_vf.c:996 xe_gt_sriov_vf_write32+0xc6/0x580 [xe] [ ] RIP: 0010:xe_gt_sriov_vf_write32+0xc6/0x580 [xe] [ ] Call Trace: [ ] <TASK> [ ] ? show_regs+0x6c/0x80 [ ] ? __warn+0x93/0x1c0 [ ] ? xe_gt_sriov_vf_write32+0xc6/0x580 [xe] [ ] ? report_bug+0x182/0x1b0 [ ] ? handle_bug+0x6e/0xb0 [ ] ? exc_invalid_op+0x18/0x80 [ ] ? asm_exc_invalid_op+0x1b/0x20 [ ] ? xe_gt_sriov_vf_write32+0xc6/0x580 [xe] [ ] ? xe_gt_sriov_vf_write32+0xc6/0x580 [xe] [ ] ? xe_gt_tlb_invalidation_reset+0xef/0x110 [xe] [ ] ? __mutex_unlock_slowpath+0x41/0x2e0 [ ] xe_mmio_write32+0x64/0x150 [xe] [ ] do_gt_reset+0x2f/0xa0 [xe] [ ] gt_reset_worker+0x14e/0x1e0 [xe] [ ] process_one_work+0x21c/0x740 [ ] worker_thread+0x1db/0x3c0 Fix that by sending H2G VF_RESET(0x5507) action instead.